Human red blood cells show submicron membrane fluctuations (CMFs) that have been mainly studied with optical microscopies. Although the functional role of this phenomenon is still uncertain, the amplitude of membrane fluctuations is considered as an indicator of mechanical resilience to the stress encountered in the capillary beds. We investigate here the membrane fluctuations in red blood cells using the scanning ion conductance microscopy (SICM), a scanning probe technique that avoids the probe-sample contact. The ion current noise was recorded at a fixed distance from the cell and converted in terms of membrane fluctuation amplitude using as a converting factor the slope of the current-distance curve. We found that CMF amplitude was irreversibly reduced by membrane cross-link. Both whole cell and local increase of membrane tension induced a reduction of CMF amplitude. As for the biochemical regulation of membrane dynamics, we observed that the activation of the noradrenergic transduction pathway, via β-receptors, increased the CMF amplitude. We conclude that the CMFs recorded by SICM and those optically recorded on red blood cells share the main features. In addition SICM provides high spatial and temporal resolution as well as the possibility to apply through the glass pipette acting as probe chemical or physical stimuli to the membrane area where the CMFs are recorded.

中文翻译：

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通过扫描离子电导显微镜中的电流信号噪声研究人红细胞的膜波动

人类红细胞表现出亚微米膜波动（CMF），主要通过光学显微镜进行研究。尽管这种现象的功能作用仍不确定，但膜波动的幅度被认为是毛细血管床中遇到的应力的机械弹性的指标。我们使用扫描离子电导显微镜（SICM）研究红细胞中的膜波动，这是一种避免探针与样品接触的扫描探针技术。在距细胞固定距离处记录离子电流噪声，并使用电流-距离曲线的斜率作为转换因子，将离子电流噪声转换为膜波动幅度。我们发现 CMF 振幅因膜交联而不可逆地降低。全细胞和局部膜张力的增加都会导致 CMF 振幅的降低。至于膜动力学的生化调节，我们观察到去甲肾上腺素能转导途径通过β受体的激活增加了CMF振幅。我们得出结论，SICM 记录的 CMF 和红细胞上光学记录的 CMF 具有共同的主要特征。此外，SICM 提供高空间和时间分辨率，并且可以通过玻璃移液管作为探针化学或物理刺激施加到记录 CMF 的膜区域。